Viral infection of the liver is a major risk factor for hepatocellular carcinoma (HCC). Natural killer (NK) cells recognize virally infected and oncogenically transformed cells, suggesting a therapeutic role for NK cell infusions in HCC. Using the K562-mb15-41BBL cell line as a stimulus, we obtained large numbers of activated NK cells from peripheral blood. Expanded NK cells exerted remarkably high cytotoxicity against HCC cells (HepG2, Hep3B, PLC/PRF/5, SNU-398, SNU-449), which was generally much higher than that of unstimulated or interleukin-2-activated NK cells. In NOD/scid IL2RGnull mice engrafted with Hep3B, treatment with expanded NK cells significantly reduced tumor growth and improved overall survival. Notably, HCC cells exposed to sorafenib, a kinase inhibitor currently used for HCC treatment, remained highly sensitive to expanded NK cells: after 48 hours with sorafenib 5 μM, cell reduction was 53.8% for Hep3B, 39.2% for SNU-449 and 42.3% for PLC/PRF/5; it climbed to 87.6%, 84.1% and 80.5% after 4 hours with NK cells at 1:1 effector-to-target ratio. NK cell cytotoxicity persisted even in the presence of sorafenib. We found that NKG2D, an NK activating receptor, was an important mediator of anti-HCC activity. We therefore enhanced its signaling capacity with a chimeric NKG2D-CD3ξ-DAP10 receptor. This considerably increased the anti-HCC cytotoxicity of expanded NK cells in vitro and in immunodeficient mice. The NK expansion and activation method applied in this study has been adapted to clinical-grade conditions. Hence, these results warrant clinical testing of expanded NK cell infusions in patients with HCC, possibly after genetic modification with NKG2D-CD3ξ-DAP10.
- Received September 11, 2015.
- Revision received March 11, 2016.
- Accepted March 28, 2016.
- Copyright ©2016, American Association for Cancer Research.